A CDMA type cellular network is constituted by a plurality of cells each having radio coverage provided by a base station. The base stations are connected to a controller. Within each cell, terminals, e.g. mobile terminals, communicate in CDMA mode with the base station of the cell, i.e. with all of the terminals using transmission in the same frequency band, and with transmitted data being spread by spreading sequences. These sequences are conventionally pseudo-random number (PN) sequences that are statistically orthogonal to one another, so as to limit interference between signals that have been spread by different sequences.
In such a cellular network, when interference within a cell increases, signal-to-noise ratio (S/N) conditions deteriorate and the base station of the cell requests each active terminal to increase the power of the signals it transits by some number of decibels (dB). The interference may come either from terminals transmitted in adjacent cells and parented on other base stations, or else be due to an increase in the number of users in the cell in question. Interference is due to a loss of statistical orthgonality between the spreading sequences because of multiple paths.
That problem is raised in PCT patent application WO 93/09626 which is fully incorporated in the present application by reference.
The drawback of that solution is that a generalized increase in the transmission power of the terminals gives rise not only to interference within the cell under consideration, but also causes increased interference in adjacent cells. The base stations of the adjacent cells will therefore also request the terminals with which they are in communication to increase their transmission powers in order to overcome the interference. Very quickly, this mechanism can therefore lead to escalation until all of the terminals throughout the CDMA network have reached maximum transmission power, thereby completely paralyzing the system.